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High-Efficiency Air Conditioner

American Superconductor (AMSC)
ARPA-E Award: 
Devens, MA
Project Term: 
05/20/2014 to 04/30/2021
Project Status: 
Technical Categories: 
Critical Need: 

New and more efficient cooling methods are needed to reduce building energy consumption and environmental impact. Buildings currently account for 72% of the nation's electricity use and 40% of our carbon dioxide (CO2) emissions each year, 5% of which comes directly from air conditioning. The refrigerants typically used in freezers are greenhouse gases (GHG) that may contribute to global climate change. Because the majority of cooling systems run on electricity, and most U.S. electricity comes from coal-fired power plants which produce CO2, there is a pressing need to support improvements that increase the efficiency of these technologies and reduce the use of GHG refrigerants.

Project Innovation + Advantages: 

American Superconductor (AMSC) is developing a freezer that does not rely on harmful refrigerants and is more energy efficient than conventional systems. Many freezers are based on vapor compression, in which a liquid refrigerant circulates within the freezer, absorbs heat, and then pumps it out into the external environment. Unfortunately, these systems can be expensive and inefficient. ITC's freezer uses helium gas as its refrigerant, representing a safe, affordable, and environmentally friendly approach to cooling. ITC's improvements to the Stirling cycle system could enable the cost-effective mass production of high-efficiency freezers without the use of polluting refrigerants. ITC received a separate award of up to $1,766,702 from the Department of the Navy to help decrease military fuel use.

Potential Impact: 

If successful, AMSC would provide Stirling cycle based freezers to the market, increasing the supply of environmental friendly, energy efficient cooling technologies.


Increased energy efficiency would decrease U.S. energy demand and reduce reliance on fossil fuels--strengthening U.S. energy security.


Refrigerants with polluting emissions could account for up to 10%-20% of global warming by year 2050. ITC's technology could eliminate the use of these refrigerants from commercial refrigeration systems.


Widespread adoption of this technology could reduce energy consumption in commercial refrigeration systems--providing commercial entities with cost savings on energy bills, which ultimately can be passed onto the consumers.

Innovation Update: 

(As of August 2016)
The ITC team initially set out to create a small-scale air conditioning system that uses low global warming potential (GWP) refrigerants while delivering a high coefficient of performance (COP) – the measure of a cooling system – at competitive cost. As their designs for air conditioning applications matured, testing revealed improved energy efficiency with the potential for use in military cooling applications. As a result, ITC has continued to develop a Stirling cycle air conditioner for extreme environments under a joint program between the Department of Defense and ARPA-E. For commercial markets, there is clear potential for use in other applications that have higher temperature differences, such as refrigeration. ITC is working with its commercial partner to take the project to the next stage of development.

ITC designed and implemented a prototype refrigeration unit using helium as the working fluid and a CO2-based external heat transfer loop, which has less GWP than current synthetic refrigerators. ITC has engaged a commercial refrigeration equipment company to assist in commercialization and test the unit. The results demonstrated a baseline COP of 1.0 with technical pathways identified to increase COP to the target value of 1.4. The system also displayed other traits desirable to refrigeration customers, including quiet operation, the ability to be deployed in a modular fashion, highly efficient and variable partial load operation, and rapid temperature pulldown.

For a detailed assessment of the ITC team's project and impact, please click here.

ARPA-E Program Director: 
Dr. Marina Sofos
Project Contact: 
Greg Buchholz
Heatcraft Worldwide Refridgeration
Release Date: